程序说明：

         线程a,b分别从字符串eg中取出一个字符，赋值给字符指针pro.

         线程c,d分别从pro中取出字符，并打印

         程序用读写锁对线程abcd进行同步

用到的读写锁函数有：

#include
     
       int pthread_rwlock_rdlock(pthread_rwlock_t *rwptr); int pthread_rwlock_wrlock(pthread_rwlock_t *rwptr); int pthread_rwlock_unlock(pthread_rwlock_t *rwptr);
     

 

 

#include 
     
      #include 
      
       #include
       
        #include
        
         #define RDNUM 2#define WRNUM 2char eg[]="I'm a test!";char *pro;struct {    int i;    pthread_rwlock_t mutex;}shared={        0,PTHREAD_RWLOCK_INITIALIZER};void pthw(){    int len=strlen(eg)+1;    int write_num=0;    for(;;){        pthread_rwlock_wrlock(&shared.mutex);        if(shared.i>=len)        {            pthread_rwlock_unlock(&shared.mutex);            break;        }        pro[shared.i]=eg[shared.i];        shared.i++;        write_num++;        pthread_rwlock_unlock(&shared.mutex);        sleep(1);    }    printf("进程%lu写了%d个字符\n",pthread_self(),write_num);}void pthr(){    int len=strlen(eg)+1;    int read_num=0;    for(;;){        pthread_rwlock_rdlock(&shared.mutex);        if(shared.i>=len&&read_num==len)        {            pthread_rwlock_unlock(&shared.mutex);            break;        }        while(read_num
        
       
      
     

运行结果：